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Show all reviews of the Cubic/Swan Astro 150A
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of the Cubic/Swan Astro 150A.
Oct 16, 2006 09:27
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One of my all-time favorites
Time owned: more than 12 months
I first encountered one of these rigs in the shack of a friend back in the late 80's; his father-in-law bought it and the matching PSU5B as for him as a present.
Eventually, the supply was sold and the radio traded throughout the family...at times residing in an over-the-road semi tractor, where it was used to check into various nets while its owner crossed the country.
I ended up with the thing at a fairly good price around 1997. It needed lots of restoration work to make it cosmetically 'presentable'. Electrically...was another story. From Day One the radio was plagued with a problem in its main VCO loop; this manifested itself as a warble in the signal (both transmitted and received).
On the shelf it went - until in early 2004 I happened to run across a Usenet bit written by Doug, WA1TUT. He described a problem with the rigs and their loop filters; seems that a rather large tantalum cap (200uF; 10v) in the Main VCO Loop filter will go bad and produce the condition that my rig was experiencing. After changing this part - voila! All fixed, and what a neat little rig it was! There's a good bit of coverage available above and below each of the amateur bands - perfect for caual SWLing and UTE monitoring. Once the rig warms up thoroughly - ~1h - it's stable enough to be used for RTTY, packet and so forth. It never drifts more than a couple hundred hertz from a cold start - very good for a rig of this design.
I was bitten...and began to buy more of them. Not perfect working examples, mind you - but old junque to resurrect.
At this point there must be a dozen or more Astro 150s hanging around my shack; most of them have their companion antenna tuners, power supplies and so forth. When Cubic took over Swan, they released this transceiver in amateur (150A) and commercial (150C) flavors. The latter could have its band coverage scheme programmed at the factory with a customer's specified ranges; I have two of the -C models and both are set up differently in this regard. (Neither were delivered as 'amateur band' transceivers but their tuning ranges still manage to cover most amateur allocations below 12M.)
The -C models used some rather hard-to-find multipin Amphenol bayonet locking connectors for such things as AFSK IN, RLY control and so forth. I've seen people remove these and convert the rear bulkhead to use standard RCA and 1/4" jacks as used on the -A models.
The little rigs are built very well and will just keep going and going. As has been pointed out before - they are NOT the equivalent of an FT1000, 756 Pro or any other fully featured HF transceiver. What they are is a set which gives the operator exactly what he or she needs to communicate; nothing more, nothing less.
A couple things to note - and be aware of - when buying and using the Astro 150 series:
First off, that tantalum cap in the VCO loop filter. If yours begins to warble, remove and swap this component. (Cubic redesigned part of the VCO Loop Filter in later-model Astros; the change decreased lock time - but the cap in question is still present. A newer-model Main VCO board looks to be missing a number of components, including an 8-pin DIP op-amp. It'll work fine in this configuration.)
Next - get hold of a service manual and verify that the foldback limiting circuitry on the RF filter board is adjusted correctly. The Astros use a PA 'brick' which is common across all of the company's product lines, so finding service info shouldn't be that difficult. The PA output transistors are MRF458 and don't have as high a dissipation rating as those used in a TR7's PA, for example. Therefore, one MUST pay attention to setup of the VSWR protection circuit - especially if driving an amp with an untuned input.
Moving on - there is a potentiometer (on the Band VCO board) which adjusts the 10.5V regulator. Setting this regulator correctly is as important for this rig's 'character' as its counterpart within a TR7 is. In other words...verify with a DVM and correct if out-of-spec.
Last - early-model PA driver transistors are spec'd as MRF433, and late-model as MRF455. If you should need to replace a '433 pair, do so with a set of '455s. The higher-gain (blue, green dot) versions of the '433 will eagerly go into thermal runaway when run in a 'stock' (non-modified) PA.
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